Digital or solid state lighting technologies, i.e., illumination based on semiconductor light sources, such as light-emitting diodes (LEDs), offer a viable alternative to traditional fluorescent, high-intensity discharge (HID), and incandescent lamps. Functional advantages and benefits of LEDs include high energy conversion and optical efficiency, durability, lower operating costs, and many others. Recent advances in LED technology have provided efficient and robust full-spectrum lighting sources that enable a variety of lighting effects in many applications.
Some of the fixtures embodying these sources feature a lighting module, including one or more LEDs capable of producing white light and/or different colors of light, e.g., red, green and blue, as well as a controller or processor for independently controlling the output of the LEDs in order to generate a variety of colors and color-changing lighting effects, for example, as discussed in detail in U.S. Pat. Nos. 6,016,038 and 6,211,626. LED technology includes line voltage powered luminaires, such as the ESSENTIALWHITE series, available from Philips Color Kinetics. Such luminaires may be dimmable using trailing edge dimmer technology, such as electric low voltage (ELV) type dimmers for 120 VAC line voltages (or input mains voltages).
Many lighting applications make use of dimmers. Conventional dimmers work well with incandescent (bulb and halogen) lamps. However, problems occur with other types of electronic lamps, including compact fluorescent lamp (CR), low voltage halogen lamps using electronic transformers and solid state lighting (SSL) lamps, such as LEDs and OLEDs. Low voltage halogen lamps using electronic transformers, in particular, may be dimmed using special dimmers, such as electric low voltage (ELV) type dimmers or resistive-capacitive (RC) dimmers, which work adequately with loads that have a power factor correction (PFC) circuit at the input.
However, conventional solid state luminaires, including LED white lighting fixtures, are input voltage dependent. Thus, the various types of solid state white lighting fixtures operate only at specific line voltages for which they are respectively designed. The value and frequency of the line voltages may differ, depending on various factors, such as geographic location of the user (e.g., U.S. markets typically require a 120 VAC, 60 Hz line voltage while European markets typically require a 230 VAC, 50 Hz line voltage) and physical location of the installed solid state white lighting fixture (e.g., fixtures installed in high alcoves typically require 277 VAC line voltage while fixtures installed in under-cabinet environments typically require 120 VAC line voltage).
Such operational differences among the various types of solid state white lighting fixtures cause confusion and practical inefficiencies for manufacturers and users. For example, electrical contractors typically must have multiple sets of inventory on hand corresponding to the number of different line voltages available in a particular construction project. The sets of inventory must be carefully managed through installation, or new LED white lighting fixtures may be ruined by application of an incorrect input line voltage. In addition, while LED white lighting fixtures designed to run at different input line voltages may have the same printed circuit boards, other components differ based on design differences needed to accommodate operation at 100 VAC, 120 VAC, 230 VAC or 277 VAC input line voltages, for example. This is inefficient from a supply chain and manufacturing perspective, since each input line voltage requires its own custom bill of materials, stock keeping units, and the like. Managing this has proved troublesome, as it is difficult to forecast demand. Therefore, marketing, supply chain and manufacturing would benefit from an LED white light or other solid state lighting fixture having a universal voltage input.
Also, conventional dimmers typically chop a portion of each waveform of the input mains voltage signal and pass the remainder of the waveform to the lighting fixture. A leading edge or forward-phase dimmer chops the leading edge of the voltage signal waveform. A trailing edge or reverse-phase dimmer chops the trailing edges of the voltage signal waveforms. Electronic loads, such as LED drivers, typically operate better with trailing edge dimmers.
Incandescent and other conventional resistive lighting devices respond naturally without error to a chopped sine wave produced by a phase chopping dimmer. In contrast, LED and other solid state lighting loads may incur a number of problems when placed on such phase chopping dimmers, such as low end drop out, triac misfiring, minimum load issues, high end flicker, and large steps in light output. Some of these problems are dependent on the dimmer setting. Therefore, to address these problems, it may be necessary to electrically determine the setting or phase angle to which the dimmer is set.